The French Encyclopædia [202] relates that M. Hassenfratz saw ice served up at table at Chambéry which broke into hexagonal prisms; and when he was shown the ice-houses where it was stored, he found considerable blocks of ice containing hexahedral prisms terminated by corresponding pyramids.

The electrostatic potential was computed using a hexahedral mesh with a grid space of 0.25 Å and the Debye-Hückel approximation to estimate the boundary conditions in the direction normal to the model membrane surface and periodic boundary conditions the membrane plane.

Patrin found long bundles of hexahedral tubes, the walls of which were formed of transverse needles: the diameter of these tubes was from two to six lines only, but at the lower extremities they opened out into hollow six-sided pyramids, more than an inch in diameter, so that the festoons, sometimes as large round as a man, presented terminal tufts of some feet in diameter, which glittered like diamonds under the influence of the torches.